Loss and repair of conjugal fertility and infectivity of the resistance factor and sex factor in Escherichia coli.

Hirota, Yukinori (University of Osaka, Osaka, Japan), Toshio Fujii, and Yukinobu Nishimura. Loss and repair of conjugal fertility and infectivity of the resistance factor and sex factor in Escherichia coli. J. Bacteriol. 91:1298-1304. 1966.-The drug-resistance factor, R, and the sex factor, F, have homologous traits, including contagious transmission, mediation of sexuality of the host cell, and autonomous replication in their host bacteria. Cooperation between F and R factors was found with a mutant R factor, which is nontransmissible in F(-) bacteria, becoming transmissible when introduced into bacteria carrying F. Conversely, the chromosome of a sterile male strain carrying the mutant sex factor, F(r), becomes transmissible when an R factor is introduced into the cell. The genetic determinants of R factors have been analyzed by isolation of mutant R factors, by sexual conjugation of the host bacteria, and by transduction of R factors with phage P1kc. The fertility determinant of the R factor, m, is inseparable from the determinant for its infectivity, but can be separated from the loci for autonomous replication of the R factor. R and F thus carry genetic determinants governing the same functions.